Tropical Storm KHANUN Advisory 10月16日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (KHANUN) WARNING NR 15//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 24W (KHANUN), LOCATED APPROXIMATELY 218 NM EAST OF HANOI,
VIETNAM, HAS TRACKED WESTWARD AT 14 KNOTS OVER THE PAST SIX
HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY SHOWS A RAPIDLY
WEAKENING SYSTEM WITH DEEP CONVECTION BECOMING DISORGANIZED AND
BEING SHEARED WESTWARD AWAY FROM THE LOW-LEVEL CIRCULATION CENTER
(LLCC). THE INITIAL INTENSITY IS SUBSEQUENTLY BROUGHT DOWN TO 65
KNOTS, WHICH MAY STILL BE SOMEWHAT GENEROUS. SURFACE OBSERVATIONS IN
ZHANJIANG AND SURROUNDING AREAS INDICATE WINDS BELOW GALE FORCE, SO
THE INITIAL INTENSITY IS BASED ON THE ASSUMPTION OF STRONGER WINDS
OVER OPEN WATER AHEAD OF THE LLCC WITHIN THE STRONGER CONVECTION.
MODERATE TO STRONG EASTERLY VERTICAL WIND SHEAR (20-25 KNOTS) IS
CURRENTLY DRIVING MOST OF THE WEAKENING, ALONG WITH LAND INTERACTION
AS THE SYSTEM ENTERS THE GULF OF TONKIN. TY 24W IS TRACKING ALONG
THE SOUTHERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING.
     A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
     B. ASSUMING THE SURFACE CIRCULATION OF TY 24W SURVIVES THE NEXT
SEVERAL HOURS, GLOBAL MODELS INDICATE A TURN TOWARD THE SOUTHWEST,
WITH LANDFALL IN VIETNAM AROUND TAU 36. GIVEN THE PERSISTENT
VERTICAL WIND SHEAR, THE SYSTEM IS NOT EXPECTED TO RECOVER ITS
INTENSITY. INSTEAD, IT WILL CONTINUE TO WEAKEN THROUGH SECOND
LANDFALL. GIVEN THE DECOUPLING OF THE CIRCULATION, THERE IS ALSO A
CHANCE THAT THE LLCC WILL CONTINUE MOVING MORE WESTWARD THAN
CURRENTLY FORECAST, LEADING TO AN EARLIER LANDFALL TO THE RIGHT OF
THE CURRENT FORECAST TRACK. GIVEN THE INTENSITY CHALLENGE, THERE IS
LOW CONFIDENCE IN THE JTWC TRACK FORECAST.//
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